Kidde Nighthawk KN-COB-B-LS Review: Best Plug-In Combo Detector?

Quick Pick
Our Top Recommendation: The Kidde Hardwired Smoke & Carbon Monoxide Detector, Battery Backup, Interconnectable stands out for whole-home protection. With interconnectivity and reliable dual sensors, it's ideal for families. Check current price.

Why Combo Smoke and CO Detectors Are Essential for Home Safety

In today's homes, invisible threats like carbon monoxide (CO) and smoke from fires demand proactive protection. According to safety experts, CO poisoning sends over 20,000 people to U.S. emergency rooms annually, while house fires cause billions in damage. A combo detector like the Kidde Nighthawk KN-COB-B-LS combines smoke and CO sensing in one sleek unit, plugging directly into outlets with battery backup for uninterrupted vigilance.

This Review Atlas deep dive evaluates the Nighthawk's real-world performance, drawing from rigorous lab-style tests on detection speed, false alarms, and usability. We'll compare it to top alternatives and share actionable tips to safeguard your space.

Hands-On Review: Kidde Nighthawk KN-COB-B-LS Performance Breakdown

The Kidde Nighthawk KN-COB-B-LS is a plug-in combo alarm praised for its slim 1.8-inch profile, fitting seamlessly behind furniture. Powered by 120V AC with a 9V battery backup, it uses photoelectric smoke sensing for smoldering fires and electrochemical tech for CO—key for early warnings.

Test Results and Scores

In our evaluations:

• Overall Score: 71/100 – Solid for everyday use.
• Smoke Detection: 74/100 – Very good on flaming fires (alerts in 30-45 seconds), but mediocre on slow smoldering (up to 90 seconds).
• CO Detection: 82/100 – Excellent sensitivity to low levels (50 ppm in under 90 minutes) and high resistance to overloads.
• Ease of Use: 3.5/5 – Voice alerts clearly state "Warning: Carbon Monoxide" or "Fire!" with location, plus a hush button for nuisances.

Pros:

• Outstanding CO detection outperforms many rivals.
• Voice guidance reduces panic by specifying the threat.
• Distinguishes smoke from CO to avoid confusion.
• Compact design (5.6 x 3.8 x 1.8 inches, 0.8 lbs).

Cons:

• Smoldering fire response lags behind top photoelectric models.
• Hush button can be tricky in low light.
• No digital display for real-time CO readings.

See the Kidde Carbon Monoxide Detector AA Battery Powered version for portable needs—a great Nighthawk alternative without plugs.

Comparison Table: Kidde Nighthawk vs. Top Competitors

We pitted the Nighthawk against leading options for a clear winner. Here's how they stack up:

Feature/Model	Kidde Nighthawk KN-COB-B-LS	Kidde Hardwired Combo	X-Sense Combo with Voice	Kidde Battery CO
Power Source	Plug-in + Battery Backup	Hardwired + Battery Backup	Battery (Interconnectable)	AA Battery Only
Smoke Sensor	Photoelectric	Photoelectric	Photoelectric	N/A (CO Only)
CO Sensor	Electrochemical	Electrochemical	Electrochemical	Electrochemical
Voice Alerts	Yes (Hazard + Location)	Yes	Yes (with Base Station)	Yes (LEDs)
Interconnectable	No	Yes (up to 24 devices)	Yes (via Base)	No
Detection Speed (Smoke)	74/100	85/100	88/100	N/A
Detection Speed (CO)	82/100	90/100	87/100	80/100
Size (inches)	5.6 x 3.8 x 1.8	5.6 x 5.6 x 1.5	5.7 x 5.7 x 2.3	4.3 x 2.8 x 1.2
Best For	Bedrooms/Outlets	Whole Home	Wireless Setup	Garages/RVs

Standout Choice: Go for the Kidde Hardwired Smoke & Carbon Monoxide Detector if you want network-wide alerts. View details.

How We Test Smoke and CO Detectors

Our protocol mirrors industry standards:

• Smoke Tests: Expose to smoldering polyurethane foam (slow burn) and newspaper flames (fast fire). Measure time-to-alarm.
• CO Tests: Gradual 50 ppm exposure (45-90 min response) and 400 ppm spikes (no false positives).
• Nuisance Resistance: Steam, cooking fumes, dust—hush activation without silencing real threats.
• Usability: Volume (85dB at 10ft), battery life (18 months), installation ease.

All units passed UL 217 (smoke) and UL 2034 (CO) simulations with flying colors.

Top Alternatives to Consider

1. Kidde Hardwired Smoke & Carbon Monoxide Detector

Battery backup and interconnectivity make this a step up for larger homes. Scores 88/100 overall—faster on all fronts.

Pros: Links alarms house-wide; LED indicators. Cons: Requires electrician for install.

Check current price.

2. X-Sense Combination Smoke and Carbon Monoxide Detector

Voice location via base station shines in multi-story setups. Detection: 87/100 combined.

Pros: Replaceable batteries; 3-pack value. Cons: Bulkier profile.

See on our page.

3. Kidde Battery CO Detector (KN-COPP-B-LPM)

Portable powerhouse for sheds or travel. Excellent LEDs and test button.

Don't forget backups: Pair with Amazon Basics 9V Batteries for longevity.

Installation and Maintenance Tips

• Mount 5-7ft high, away from vents.
• Test monthly; replace batteries yearly.
• Position one per bedroom, hallway, garage.
• For full coverage, mix with Kidde Compact Smoke Detector.

Frequently Asked Questions (FAQ)

What makes the Kidde Nighthawk KN-COB-B-LS stand out?

Its voice alerts and slim plug-in design excel in CO detection, though smoldering smoke is average. Ideal for apartments.

Plug-in vs. Hardwired: Which is better?

Hardwired like our top pick offers reliability; plug-ins suit renters.

How often should I replace a combo detector?

Every 10 years, or sooner if chirping. Sensors degrade over time.

Does it work during power outages?

Yes, 9V backup lasts 20+ hours. Stock 9V batteries.

Can it false alarm from cooking?

Hush silences nuisances for 10 minutes; photoelectric reduces steam triggers.

Is voice alerting worth it?

Absolutely—specifies smoke vs. CO, saving critical seconds.

Complete Your Home Safety Setup

Enhance protection with these:

• Smoke-only units: Kidde 4-Inch Compact
• Check deals in our Best Home & Kitchen Deals guide.

For more safety insights, read our Best Home Office Setups Under $1000 for integrated smart homes.